The United States and Japan will step up their defence cooperation to deal with the threat from nuclear-armed North Korea as tensions in East Asia remain high, officials from the two allies said on Thursday.

WA hospital to help patients regrow skulls

Patients needing cranial reconstructions will have parts of their own skulls regrown using a new procedure involving stem cells and advanced 3D printing technology.

The procedure will be performed at Royal Perth Hospital on patients whose skulls have been severely damaged, or have had a piece removed to enable surgery or relieve pressure caused by swelling of the brain.

Biomedical materials engineer Alan Kop said surgeons would have previously used a titanium plate, which was sometimes a source of infection, or plastic or ceramics as an alternative to the patient's original bone.

He said it would be better for the patient to regrow their own bone.

The team at RPH also includes a surgeon, neurosurgeon and principal scientist who have been working with a company in Vienna on the 3D printing technology.

Dr Kop said clinical trials would begin next year on patients who volunteered for the procedure.

"Hopefully, it will become commonplace," he told AAP.

The project is being funded with the help of a WA government research grant, which also includes funding for eight other health projects totalling almost $2 million.